Controlled-release composition having a membrane comprising submicron particles

Abstract

Novel controlled-release compositions are disclosed. These compositions comprise: (1) an agent suitable for use in a selected environment; and (2) a membrane surrounding this agent. The membrane is substantially inert to the agent and permeable to the environment, its thickness and permeability comprising a means for controlling diffusion of the environment therethrough. The membrane thickness is substantially uniform due to the presence of a quantity of submicron particles therein, these particles being substantially inert to the membrane and the agent. The membrane comprising the submicron particles is capable of releasing the agent to the selected environment at a predetermined time by a variety of mechanisms. The release mechanisms that may be selected for use with a composition will depend in part on the choices of agent, membrane, and submicron particle materials, as well as on the choice of environment into which the composition is to be introduced.

We claim: 
     
       1. A composition comprising: (1) an agent suitable for use in a selected environment; and   (2) a membrane surrounding the agent, the membrane being substantially inert to the agent and permeable to the environment, the thickness and permeability of the membrane comprising a means for controlling diffusion of the environment therethrough, the membrane further comprising submicron particles that are substantially inert to the membrane and the agent, such that the membrane is capable of releasing the agent to the environment.   
     
     
       2. The composition of claim 1 wherein the environment is aqueous. 
     
     
       3. The composition of claim 1 wherein the agent is a solid particle. 
     
     
       4. The composition of claim 1 wherein the agent is a liquid. 
     
     
       5. The composition of claim 4 wherein the liquid is absorbed into a solid porous particle. 
     
     
       6. The composition of claim 5 wherein the solid porous particle is porous sodium chloride. 
     
     
       7. The composition of claim 1 wherein the agent has a diameter within the range of from about 0.05 mm to about 3 mm. 
     
     
       8. The composition of claim 1 wherein the agent has a diameter within the range of from about 0.5 mm to about 2 mm. 
     
     
       9. The composition of claim 1 wherein said agent reacts with said environment to liberate at least one gas selected from the group consisting of oxygen, hydrogen, carbon dioxide, nitrogen, and mixtures thereof. 
     
     
       10. The composition of claim 1 wherein the agent is an oxidizing agent. 
     
     
       11. The composition of claim 10 wherein the oxidizing agent is a bleach. 
     
     
       12. The composition of claim 1 wherein the bleach is selected from the group consisting of magnesium monoperoxyphthalate hexahydrate, ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, sodium hypochlorite, lithium hypochlorite, sodium peroxide, sodium chlorite, calcium hypochlorite, hypochlorous acid, chlorinated lime, sodium perborate, organic chlorine derivatives, potassium perphosphate, and mixtures thereof. 
     
     
       13. The composition of claim 1 wherein the membrane has a thickness within the range of from about 5 μm to about 40 μm. 
     
     
       14. The composition of claim 1 wherein the membrane has a thickness within the range of from about 5 μm to about 25 μm. 
     
     
       15. The composition of claim 1 wherein the membrane comprises a material selected from the group consisting of polystyrene latex, styrene-butadiene rubber, neoprene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene dichloride, ethylene acrylic acid, polystyrene, polycarbonate, cellulose esters, glycolide/lactide copolymers, lacquers, cellulose ethers, starches, chemically modified starch products, colloidal suspensions, monomeric vapor coatings, plasma generated materials, and mixtures thereof. 
     
     
       16. The composition of claim 1 wherein the membrane comprises a latex coating. 
     
     
       17. The composition of claim 1 wherein the submicron particles are selected from the group consisting of aqueous colloidal silica, fumed silica, fumed alumina, fumed magnesia, fumed calcia, fumed carbon, fumed titania, polytetrafluoroethylene, and mixtures thereof. 
     
     
       18. The composition of claim 1 wherein the submicron particles are present in an amount within the range of from about 0.1 ppm to about 50,000 ppm relative to the membrane. 
     
     
       19. The composition of claim 1 wherein the submicron particles are present in an amount within the range of from about 1 ppm to about 5,000 ppm relative to the membrane. 
     
     
       20. The composition of claim 1 wherein the diffusion is osmotic. 
     
     
       21. A fabric laundering composition comprising: at least one part of a fabric laundering formulation admixed with at least one part of a composition comprising:   (1) an oxidizing agent suitable to react with an aqueous environment to liberate a gas; and   (2) a membrane surrounding the oxidizing agent, the membrane being substantially inert to the agent and permeable to the environment, the thickness and permeability of the membrane comprising a means for controlling diffusion of the environment therethrough to permit reaction of the agent with the environment, the membrane further comprising submicron particles that are substantially inert to the membrane and the oxidizing agent, such that the membrane is capable of releasing the agent to the environment.   
     
     
       22. The composition of claim 21 wherein the laundering formulation comprises a detergent and an enzyme cleaner, a fabric softener, a fabric whitening composition, or a mixture thereof. 
     
     
       23. The composition of claim 21 wherein the oxidizing agent is a bleach selected from the group consisting of magnesium monoperoxyphthalate hexahydrate, ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, sodium hypochlorite, lithium hypochlorite, sodium peroxide, sodium chlorite, calcium hypochlorite, hypochlorous acid, chlorinated lime, sodium perborate, organic chlorine derivatives, potassium perphosphate and mixtures thereof. 
     
     
       24. The composition of claim 21 wherein the membrane comprises a material selected from the group consisting of polystyrene latex, styrene butadiene rubber, neoprene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene dichloride, ethylene acrylic acid, polystyrene, polycarbonate, cellulose esters, glycolide/lactide copolymers, lacquers, cellulose ethers, starches, chemically modified starch products, colloidal silica, colloidal sulfur, monomeric vapor coatings, plasma generated materials, and mixtures thereof. 
     
     
       25. A method of producing a controlled release composition comprising: (1) selecting an agent suitable for use in a selected environment; and   (2) surrounding the agent with a membrane, the membrane being substantially inert to the agent and permeable to the environment, the thickness and permeability of the membrane comprising a means for controlling diffusion of the environment therethrough, the membrane further comprising submicron particles that are substantially inert to the membrane and the agent, such that the membrane is capable of releasing the agent to the environment.   
     
     
       26. The method of claim 25 wherein the agent is an oxidizing agent. 
     
     
       27. The method of claim 25 wherein the membrane comprises a latex coating. 
     
     
       28. The method of claim 25 wherein the submicron particles are selected from the group consisting of aqueous colloidal silica, fumed silica, fumed alumina, fumed magnesia, fumed calcia, fumed carbon, fumed titania, polytetrafluoroethylene, and mixtures thereof. 
     
     
       29. In a controlled release composition comprising: (1) an agent suitable for use in a selected environment; and   (2) a membrane surrounding the agent, the membrane being substantially inert to the agent and permeable to the environment, the thickness and permeability of the membrane comprising a means for controlling diffusion of the environment therethrough, such that the membrane is capable of releasing the agent to the environment;   an improvement comprising the membrane further comprising submicron particles that are substantially inert to the membrane and the agent.